This application claims priority to International Application No. PCT/DE00/00171 which was published in the German language on Aug. 3, 2000.
The invention relates to a one-component epoxy resin adhesive, and in particular, to a one-component epoxy resin adhesive which is elasticated with silicone rubber and whose open joint time can be adapted.
In many sectors of industry, workpieces are already fastened or joined exclusively by adhesive bonding. This is typically at the expense of conventional fastening techniques such as welding, soldering, threaded union, or the like. The continually growing fields of use demand adhesives which in turn are required to satisfy a wide variety of requirements.
DE 195 38 468 A1 discloses a one-component adhesive with a favorable profile of properties. However, its highly reactive UV initiator does not allow an industrially practical open joint time, and its lack of elasticating particles also renders it unsuitable for extensive (i.e., large surface area) bonds.
The invention relates to a one-component epoxy resin adhesive which is elasticated with silicone rubber and whose open joint time can be adapted to whichever production process it is used in via the nature and concentration of the photoinitiator and/or the duration and/or intensity of UV activation. This adhesive is preferentially suitable for automated adhesive bonding processes and may also be used with advantage for adherents of large surface area having opposite thermal expansion coefficients. It is suitable, for example, for adhesive bonds of permanent magnet materials, such as in the assembly of permanent magnets on metal pole plates and/or solid steel poles in machines with permanent-magnet excitation.
The invention provides an adhesive and a method of adhesive bonding which can be used to realize industrially practical open joint times and extensive bonds.
Furthermore, the use of adhesives which form an elastic adhesive bond is on the increase, especially when the bonded union produced is to be thermally stable over a wide temperature range, since on heat-induced expansion or shrinkage of the workpieces the adhesive bond ought to compensate differences in length by virtue of its elasticity.
The invention provides a one-component adhesive comprising:
A) 5-90% by weight of a cycloaliphatic epoxy resin component,
B) 10-94% by weight of an epoxy-functional silicone rubber,
C) 0.05-5% by weight of a ferrocene-based UV initiator,
D) 0.1-5% by weight of a thermal initiator,
E) 0.05-1.5% by weight of an adhesion promoter,
F) 0.1-10% by weight of a highly disperse silica,
G) 0-3% by weight of spacers, and
H) 0-70% by weight of filler.
The invention further provides a method of two-dimensionally adhesively bonding two workpieces, which comprises:
applying a film of an adhesive to one of the two workpieces or to both workpieces,
setting a desired open joint time of the adhesive by duration-and intensity-specific UV irradiation and/or heat treatment and/or IR irradiation, for the purpose of positional fixing, and
joining the two workpieces,
thermally aftercuring the adhesive.